Hybrid PowertrainThe RX 450h’s Lexus Hybrid Drive features a 3.5-liter V6 Atkinson-cycle engine, electric motors, a small and light power-control unit and other fuel-saving innovations. It offers performance similar to V8s, 295 total system horsepower and in many cases better combined fuel economy than the average four-cylinder mid-size sedan.

As a full hybrid, the 2012 Lexus RX 450h can operate in electric-only or gas-engine-only modes as well as a mode that combines the power of both. Extended electric-mode operation during low-speed or stop-and-go driving conditions helps reduce fuel consumption. Under certain circumstances, a driver-selectable EV mode can allow the vehicle to be driven short distances using only the electric motors.

A cooled Exhaust Gas Recirculation (EGR) system reduces it further still, helping economy by eliminating the fuel enrichment otherwise needed to help prevent catalyst overheating under high loads.

A compact 288V DC Nickel Metal Hydride (Ni-MH) battery pack fits neatly under the rear seat. A boost converter efficiently raises voltage to 650V DC, and an inverter changes this to 650V AC for the front-mounted 123-kW electric motor-generator. The boost converter and inverter are enclosed in the power-control unit, which also houses the condenser.

The RX 450h FWD model’s hybrid powertrain employs two motor-generators: MG1, the engine-driven generator, is a starter and can charge the battery pack or power other electric motors as needed; MG2 is the front-drive motor. Power from the gas engine and MG2 is distributed to the drive wheels via a planetary gear-type continuously variable transmission. MG1 controls the output speed of the transaxle through the planetary gear set, without clutches or a viscous coupling. MG2 delivers torque over a wide range for better response and smooth performance. When the RX 450h is coasting or braking, the electric motors function as generators, capturing energy that would normally be lost as heat through the brakes and transforming it into electricity to recharge the batteries.

RX 450h AWD adds a third, rear-mounted motor-generator (MGR) to drive the rear wheels, eliminating the need for power-transfer gearing or a driveshaft from the front. The hybrid system electronically varies front and rear torque distribution depending on traction conditions. A two-step flywheel damper absorbs small torque fluctuations and also the minor vibration produced when the gasoline engine starts and stops. A SNOW mode slows accelerator-pedal response to help reduce the possibility of wheel spin.

Multi-Mode, a feature adapted to the vehicle’s electronically controlled continuously variable transmission, allows the driver to control engine braking for enhanced maneuverability on rough or winding roads. The Intelligent Shift Control feature selects and holds the optimal range when driving downhill or on inclines, providing a smoother driving experience.

The 2012 RX 450h AWD uses a separate rear electric motor-generator to provide power to the rear wheels when road conditions or throttle response dictates. When accelerating, or starting off on a low-grip surface, torque is quickly provided to all four wheels. At steady speeds, torque is sent only to the front wheels, enhancing fuel efficiency. For handling agility and control, the AWD system increases rear-wheel torque when the vehicle’s front tires start to lose traction and decreases rear-wheel torque when the vehicle’s rear tires start to lose traction.

SafetyThe RX 450h features Intelligent Adaptive Front-lighting System (AFS) for high beams of HID headlamp equipped models, and for the low beams of the LED equipped models. When entering a corner, AFS estimates where the vehicle will be based on the vehicle speed and the angle of the tires, and adjusts the lateral aim of the headlamps. AFS can be switched off by the driver if desired and includes an auto-leveling function.

Also available is an automatic high beam system which uses a camera mounted on the inner rear view mirror to switch between high and low beams in response to oncoming vehicles and those traveling in front, or when other ambient sources are detected, helping reduce driver inconvenience.

The optional Pre-Collision System (PCS) with Dynamic Radar Cruise Control uses millimeter-wave radar to measure and help maintain a pre-set following distance from a vehicle traveling ahead. The radar sensor can detect certain obstacles in front of the car, and a PCS computer with vehicle speed, steering angle and yaw-rate inputs helps to determine whether a collision is highly possible. In such a situation, PCS preemptively retracts front seat belts and pre-initializes BA so that increased braking will be applied the instant the driver depresses the pedal.

The RX 450h is equipped with a segment-leading 10 standard airbags, including side curtain airbags, front seat-mounted side airbags, rear side airbags (for the outboard seating positions) and knee airbags for the driver and the front passenger. A roll sensor signals the side curtain airbags to inflate if a predetermined threshold of vehicle tip-up is detected.

Luxury OptionsAn available 12-speaker system audio system comes with the optional Comfort Package or rear seat entertainment systems and includes two-rear-door tweeters and a compact, L-shaped subwoofer in the rear-luggage compartment.

Lexus RX 450h owners will also enjoy all of the typical RX benefits, including class-leading interior quality and an impressively smooth and quiet ride. The cabin also boasts a bevy of high-tech features -- both standard and optional -- to please most technology enthusiasts, including a surprisingly useful mouselike electronics interface, a sweet-sounding Mark Levinson sound system and LED headlamps.The optional 15-speaker Mark Levinson Surround Sound system allows listeners to enjoy 330 watts at 0.01 percent THD through 7.1-channel surround sound. The Mark Levinson system, a Lexus exclusive, features a center channel coaxial speaker, metal-cone midrange speakers, tweeters and a 100-watt amplified subwoofer. A 2.5-inch speaker built into each D-pillar provides the right and left surround-sound channels. The diffusion of sound provides each occupant the same level of audio quality.

2012 Lexus RX 450h also offers a telematics system, Lexus Enform with Safety Connect, available by subscription. Complimentary one-year trial subscriptions are included on all purchases of new Lexus vehicles equipped with these features. Safety Connect is standard on all vehicles while Lexus Enform with Safety Connect is on all vehicles equipped with the optional Navigation system. The Lexus Enform and the Safety Connect response centers operate 24 hours a day, 7 days a week—every day of the year.